The correct answer isAllahabad.

(Prayagraj)Allahabad is not a capital of any state.

• The city of Prayagraj is among the largest cities of Uttar Pradesh and situated at the confluence of three rivers- Ganga, Yamuna, and the invisible Saraswati.
• Allahabad city's name was changed to Prayagraj on 16th October 2018.
• In 1868, itbecame a seat of Justice when Allahabad High Court was established.
• In 1887, Prayagraj became a seat of knowledge with the establishment of the fourth oldest University –the University of Allahabad.
• Prayagraj has provided the largest number of prime ministers of Post-independence India.